Tractor-trailers generally include a floor assembly supporting a container. The container includes sidewalls, which can be made up of multiple wall panels coupled to each other and to base rails of the floor assembly, often by rivets. Rivets can support both tensile loads (i.e., loads parallel to an axis of the rivet shaft) and shear loads (i.e., loads perpendicular to the rivet shaft axis). Generally, conventional solid bucking rivets 100, such as the one shown in FIGS. 1A-1C, are used. While the bucked side of each rivet is usually positioned against the metal base rail (that is, opposite the wall panel), some applications require the bucked side to be positioned against the wall panel.
Wall panels are generally made of composite materials that can be constructed of, for example, a plastic core positioned between and bonded to two metal skins. When the bucked side 102 of a rivet 100 is positioned against the wall panel 104 rather than the base rail 106, as shown in FIG. 1B, forces applied to the rivet 100 or the wall panel 104 can cause the core material to stretch and the metal skin to deform, thus enlarging a hole or channel 108 through which the rivet 100 is inserted. For example, forces against the wall panel 104, such as from items in the container pushing against the wall panel 104, can cause the wall panel 104 to push away from the rivet 100. As shown in FIG. 1C, this causes the hole 108 to enlarge as the bucked side 102 is pulled through the wall panel 104, thus uncoupling the wall panel 104 from the base rail 106.
Under conventional thinking, one solution to the above-described rivet push-off problem is to apply more force when setting the solid rivets, thus increasing the diameter of the bucked head and providing a steeper angle between the bucked head and the metal skin. However, contrary to the conventional understanding of rivet assembly in the industry, it has recently been found that the additional force applied against the bucked head often causes the core material to stretch, thereby enlarging the hole housing the rivet and thus exacerbating the original problem. Another solution to the rivet push-off problem is to use a softer rivet. However, while softer rivets can prevent pull-out due to tensile loads, they lack the shear strength necessary to handle imposed shear loads.
Yet another solution to the rivet push-off problem is to use tubular (or semi-tubular) rivets 120, as shown in, for example, FIG. 2A. The tubular rivets 120 generally include a shaft 122, a head 124 positioned at a first end of the shaft 122, and a tail 126 formed at a second end of the shaft 122. A cavity 128 is formed in the tail 126, the cavity 128 having a diameter that is less than a diameter of the tail 126, thereby forming a circumferential portion 130 that can be rolled outwardly during setting. Typically, the circumferential portion 130 of tubular rivets 120 is thin to provide for ease in setting. For example, a diameter of the cavity 128 may be ¾ or more of a diameter of the shaft 122. A setting tool 132 for bucking or setting the rivets 120 of FIG. 2A is depicted in FIG. 2B. The setting tool 132 has an edge 134 that has a central projection and curved edges extending from the central projection to generally form a wave. During setting the rivets 120, the central projection of each tool 132 (a tool is needed for each rivet) is aligned with the cavity 128 and outer portions of the tool 132 cause the circumferential portion 130 to roll outward into contact with the surface to which the rivets 120 are attached. The problem with such rivets 120 is that these specialized setting tools 132 are necessary to ensure the bucked head is set properly (i.e., that edges of the bucked head properly roll radially outward). As a result, such rivets (having a relatively think circumferential portion 130) cannot effectively be set using current setting processes like flat presses without deforming the rivet and rendering it useless. More specifically, without the formed rivet dies, tubular rivets often roll off-center during bucking, causing a weaker coupling. Furthermore, even with special tooling, multiple tubular rivets cannot be set simultaneously unless the rivets are specifically spaced apart to correspond to mating rivet dies on the special tooling. In container applications, rivets are generally not aligned perfectly horizontally or vertically, making it unfeasible to use these special tooling pieces for multiple rivets simultaneously. Thus, conventional tubular rivets require additional setting time and additional costs for special tooling.